Surprise!

Richard A. Posner writes,

it is almost impossible to take effective action to prevent something that hasn't occurred previously. Once the 9/11 attacks did occur, measures were taken that have reduced the likelihood of a recurrence. But before the attacks, it was psychologically and politically impossible to take those measures...

The problem isn't just that people find it extraordinarily difficult to take novel risks seriously; it is also that there is no way the government can survey the entire range of possible disasters and act to prevent each and every one of them...

Illustrating the psychological and political difficulty of taking novel threats seriously, the commission's recommendations are implicitly concerned with preventing a more or less exact replay of 9/11.

Absolutely. But we've got to blame someone.